Pneumatic cylinder plug

ABSTRACT

A pneumatic cylinder plug has an annular body, an axial through hole, an inside flange, an outside flange, an air port, an inner bushing and an air gap. The through hole is defined through the annular body. The air port is formed radially through the annular body and the inside flange from the axial through hole to the outside surface of the annular body. The inner bushing is formed inside the inner flange and has an inner diameter. The pneumatic cylinder plug is used with a closed pneumatic device to further support a piston rod in the closed pneumatic device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cylinder plug, and more particularly to a plug to slidably mount a pneumatic cylinder on a piston rod and to provide a port to one side of a pneumatic piston mounted in the pneumatic cylinder.

2. Description of Related Art

Closed pneumatic devices have a simple structure and are used in adjustable furniture, medical appliances, bicycles, motorcycles, vehicles, etc. For example, some adjustable chairs, as used in offices, use a closed pneumatic device to adjust the height of the seat of the chair.

With reference to FIG. 3, one embodiment of a conventional closed pneumatic device used to adjust the position of an object, has a cylinder assembly (30), a cross-connect valve (not shown), a bushing (60), a hermetic seal (50), a cylinder plug (40), and a piston assembly (20).

The cylinder assembly (30) has an inner cylinder (31), an outer cylinder (32), an air passage (33) and an end cap (34). The inner cylinder (31) has a top end, a bottom end and an internal chamber. The outer cylinder (32) is mounted around the inner cylinder (31) and has a distal end (not shown) and a proximal end. The air passage (33) is defined between the inner cylinder (31) and the outer cylinder (32) and communicates with the internal chamber. The end cap (34) is mounted at the proximal end of the outer cylinder (32) and has a central hole.

The cross-connect valve is mounted in the inner cylinder (31) near the top end and selectively communicates between the inner chamber and the air passage (33).

The bushing (60) is mounted inside the end cap (34) adjacent to the proximal end of the outer cylinder (32).

The hermetic seal (50) is mounted inside the outer cylinder (32) between the bottom end of the inner cylinder (31) and the bushing (60).

With further reference to FIG. 4, the cylinder plug (40) has an axial through hole (41), an annular body (42), an inside flange (43), an outside flange (44) and an air port (45). The axial through hole (41) has a diameter. The annular body (42) has an inside end, an outside end, an outside surface. The inside flange (43) is formed on and extends longitudinally inward from the inside end of the annular body (42) and has an inside end and multiple inside notches (431). The inside notches (431) are defined on the inside end of the inside flange (43).

The air port (45) is formed radially through the annular body (42) and the inside flange (43) from the axial through hole (41) to the outside surface of the annular body (42).

The piston assembly (20) has a piston rod (22) and a piston (21). The piston rod (22) has an inside end, an outside end and an outside diameter and extends slidably through the proximal end of the outer cylinder (32), the central hole in the end cap (34), the central hole in the bushing (60), the central hole in the hermetic seal (50) and the axial through hole (41) in the cylinder plug (40). The outside diameter of the piston rod (22) is smaller than the diameter of the axial through hole (41). The piston (21) is connected to the piston rod (22) and is slidably mounted in the inner cylinder (31) to divide the internal chamber into two separate air chambers.

When the internal chambers are isolated by the cross-connect valve, the piston assembly (20) and the cylinder assembly (30) are held in position relative to each other. The position is changed by opening the cross-connect valve to allow air in the air chambers to freely flow between the air chambers so the position of the piston assembly (20) can be easily changed relative to the cylinder assembly (30).

When the opened cross-connect valve is opened to make the internal chambers communicate with each other, the air pressures respectively in the internal chambers are equal and allow the cylinder assembly (30) to slide longitudinally around the piston assembly (20).

However, the piston rod (22) is supported merely by the bushing (60). When cylinder assembly (30) slides back and forth around the piston assembly (20), the bushing (60) is eventually worn down by the piston rod (22) and fails to hold the piston rod (22), which makes the closed pneumatic device inoperable. Therefore, the closed pneumatic device is not durable.

To overcome the shortcomings, the present invention provides a pneumatic cylinder plug to mitigate or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

The main objective of the invention is to provide a pneumatic cylinder plug that supports a piston rod inside a cylinder and keeps the piston rod sliding along a straight line from becoming misaligned.

A pneumatic cylinder plug in accordance with the present invention comprises an annular body, an axial through hole, an inside flange, an outside flange, an air port and an inner bushing.

The inner bushing is formed inside the inner flange and has an inside diameter.

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged view in partial cross section of a closed pneumatic device with a pneumatic cylinder plug in accordance with the present invention;

FIG. 2 is a perspective view in partial cross section of the pneumatic cylinder plug in FIG. 1;

FIG. 3 is an enlarged view in partial cross section of a cylinder with a conventional pneumatic cylinder plug in accordance with the prior art; and

FIG. 4 is a perspective view in partial cross section of the pneumatic cylinder plug in FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference to FIGS. 1, a pneumatic cylinder plug (10) in accordance with the present invention is used with a conventional closed pneumatic device.

The closed pneumatic device has a cylinder assembly (30′), a cross-connect valve (not shown), a bushing (60′), a hermetic seal (50′) and a piston assembly (20′).

The cylinder assembly (30′) has an inner cylinder (31′), an outer cylinder (32′), an air passage (33′) and an end cap (34′). The inner cylinder (31′) has a top end (not shown), a bottom end and an internal chamber. The outer cylinder (32′) is mounted concentrically around the inner cylinder (31′) and has a distal end (not shown) and a proximal end. The air passage (33′) is defined between the inner cylinder (31′) and the outer cylinder (32′) and communicates with the internal chamber. The end cap (34′) is mounted at the proximal end of the outer cylinder (32′).

The cross-connect valve is mounted in the inner cylinder (31′) near the top end and selectively communicates between the internal chamber and the air passage (33′).

The bushing (60′) is mounted inside the end cap (34′) at the proximal end of the outer cylinder (32′) and has a central hole formed longitudinally through the bushing (60′).

The hermetic seal (50′) is mounted inside the outer cylinder (32′) against the bushing (60′) and has a central hole formed longitudinally through the hermetic seal (50′).

The piston assembly (20′) has a piston rod (22′) and a piston (21′). The piston rod (22′) has an inside end, an outside end (not shown) and an outside diameter and extends slidably through the proximal end of the outer cylinder (32′), the central hole in the end cap (34′), the central hole in the bushing (60′) and the central hole in the hermetic seal (50′). The inside end of the piston rod (22′) is connected to the inside end of the piston (21′).

The piston (21′) is connected to the inside end of the piston rod (22′), is slidably mounted in the inner cylinder (31′) and divides the internal chamber into two separate air chambers.

With further reference to FIG. 2, the pneumatic cylinder plug (10) in accordance with the present invention is mounted around the piston rod (22′) between the bottom end of the inner cylinder (31′) and the hermetic seal (50′) and comprises an annular body (12), an axial through hole (11), an inside flange (13), an outside flange (14), at least one air port (15), an inner bushing (16) and an air gap (17). The annular body (12) has an inside end, an outside end and an outside surface. The axial through hole (11) is defined through the annular body (12) and is mounted slidably around the piston rod (22′). The inside flange (13) is formed on and extends longitudinally inward from the inside end of the annular body (12) and has an inside end and multiple inside notches (131). The inside notches (131) are defined on the inside end of the inside flange (13). The outside flange (14) is formed on and extends longitudinally from the outside end of the annular body.

The at least one air port (15) is formed radially through the annular body (12) and the inside flange (13) from the axial through hole (11) to the outside surface of the annular body (12) and has a bottom port surface defined inside the at least one air port (15).

The inner bushing (16) is formed inside the inner flange (13), is mounted around the piston rod (22′) and has an inner diameter. The inner diameter of the inner bushing (16) is slightly larger than the outer diameter of the piston rod (22′).

The air gap (17) is defined inside the at least one air port (15) between the bottom port surface and the inner bushing (16) and allows the at least one air port (15) to communicate with the axial through hole (11) in the annular body (12).

To work the closed pneumatic device, high-pressure air needs to be injected into the conventional closed pneumatic device when all components and the cylinder plug have been assembled without the end cap (34′) and the bushing (60′). The high-pressure air is injected through the central hole in the hermetic seal (50′) into the axial through hole (11) in the annular body (12). The air gap (17) in the annular body (12) allows the high-pressure air to pass efficiently into the air passage (33′) and the internal chamber. Without the air gap, injecting high-pressure air into the conventional closed pneumatic device is inefficient.

The pneumatic cylinder plug (10) in accordance with the present invention includes all functions of the cylinder plug (40) described in the description of related art and further has the inner bushing (16) to hold the piston rod (22′) to slide along a straight line relative to the cylinder assembly (30′) and keep the piston rod (22′) from tilting.

The piston rod (22′) is supported simultaneously by the bushing (60′) and the inner bushing (16) to slide along a straight line relative to the cylinder assembly (30′). The durability of the closed pneumatic device is improved. Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A pneumatic cylinder plug comprising: an annular body having an inside end, an outside end and an outside surface; an axial through hole defined through the annular body; an inside flange formed on and extending longitudinally from the inside end of the annular body and having an inside end; and multiple inside notches defined on the inside end of the inside flange; an outside flange formed on and extending longitudinally from the outside end of the annular body; at least one air port formed radially through the annular body and the inside flange from the axial through hole to the outside surface of the annular body and having a bottom port surface; and an inner bushing formed inside the inner flange and having an inner diameter.
 2. The pneumatic cylinder plug as claimed in claim 1 further having an air gap defined inside the air port between the bottom port surface and the inner bushing and allowing the air port to communicate with the axial through hole in the annular body.
 3. A central position seat comprising: an annular body having an inside end, an outside end and an outside surface; an axial through hole defined through the annular body; an inside flange formed on and extending longitudinally from the inside end of the annular body and having an inside end; and multiple inside notches defined on the inside end of the inside flange; an outside flange formed on and extending longitudinally from the outside end of the annular body; at least one air port formed radially through the annular body and the inside flange from the axial through hole to the outside surface of the annular body and having a bottom port surface; and an inner bushing formed inside the inner flange and having an inner diameter.
 4. The central position seat as claimed in claim 3 further having an air gap defined inside the air port between the bottom port surface and the inner bushing and allowing the air port to communicate with the axial through hole in the annular body. 